Terra-Dome Earth Shelter Build

[dave1949]

I've revised my thoughts on payback for the solar panels--it will happen this winter. We spent $4k on propane last winter, I expect 9 panels to cost half that much.

In your case with passive solar, what you have is a large time lag due to the concrete. Heat out = heat in, this doesn't cost any extra energy, just slows things down. Maybe there is an efficiency effect on your boiler though.

If I were to do this again, I'd put more than 2" insulation under the concrete floors, and more around the edges.

On the other hand, comparing notes with others in our area, last winter people did use more propane than usual.

Steve

Are you as earth-buried now as you will be? That is a lot of propane. Are you burning any wood?

One thing about radiant heat in a thick slab, I think it's best to get the thermostats that have a temp sensor embedded in the concrete floor slab. I notice the bathroom I heat with radiant "overshoot's" the thermometer setting considerably just sensing air temp 5' above the floor.

I could get more consistent heat and cheaper operation by just cycling that zone a fixed amount of time once a day. Would have to play with the timing to zero in. I know people with radiant heat who do this, even though the advice is always to just leave it set. With an in-floor sensor and thin slab, that probably is good advice. With an 8" slab and and air sensing, it isn't.
Dave.

 

[sajurcaju]

Are you as earth-buried now as you will be? That is a lot of propane. Are you burning any wood?

One thing about radiant heat in a thick slab, I think it's best to get the thermostats that have a temp sensor embedded in the concrete floor slab. I notice the bathroom I heat with radiant "overshoot's" the thermometer setting considerably just sensing air temp 5' above the floor.

I could get more consistent heat and cheaper operation by just cycling that zone a fixed amount of time once a day. Would have to play with the timing to zero in. I know people with radiant heat who do this, even though the advice is always to just leave it set. With an in-floor sensor and thin slab, that probably is good advice. With an 8" slab and and air sensing, it isn't.
Dave.

No wood yet, we hope to get the wood stove installed by this fall. That will help.

We've got a 4" slab, air sensing thermostats with slab sensors to limit slab temp. Typically, overshoot is 2 degrees or less. I don't know if our thermostats are smart enough to deal with the slab heat or if our setup just happens to work.

Steve

 

[sajurcaju]

I should add that we prices aren't great--$3.70-$4 per gallon. Not that the suppliers are all in cahoots or anything.

Steve

 

[dave1949]

No wood yet, we hope to get the wood stove installed by this fall. That will help.

We've got a 4" slab, air sensing thermostats with slab sensors to limit slab temp. Typically, overshoot is 2 degrees or less. I don't know if our thermostats are smart enough to deal with the slab heat or if our setup just happens to work.

Steve

You have the right kind of thermostat setup IMO.

Did you get any feel for what temperature your house would stabilize at without adding heat? I think a wood burner would make a huge difference.

Ouch on the propane prices. I contracted ahead at with Downeast Energy for $2.699/gal for this past season. Season before I contracted at $2.199/gal. Their minimum contract is supposedly for 500 gal/yr. I only use about 400 gal. and they have been okay with that. The bulk of my propane goes to domestic hot water. I really ought to go solar for that.

Pre-paid contracts are a crap shoot price-wise and you have to really trust the supplier. For the past couple years it seems a few oil suppliers have gone bankrupt leaving their pre-paid customers in a bad way. I don't know if they get in over their heads with futures contracts or what.

I have used an electric space heater to take the chill off the shower bathroom just running it for 45 min. or so when showering, which is much cheaper (<20 cents/day), but we thought we would see what the radiant heat will do. It adds about 80 gals of propane to my annual usage but the floor is warm - which makes Sharon happy

Dave.

 

[sajurcaju]

You have the right kind of thermostat setup IMO.

Did you get any feel for what temperature your house would stabilize at without adding heat? I think a wood burner would make a huge difference.

Ouch on the propane prices. I contracted ahead at with Downeast Energy for $2.699/gal for this past season. Season before I contracted at $2.199/gal. Their minimum contract is supposedly for 500 gal/yr. I only use about 400 gal. and they have been okay with that. The bulk of my propane goes to domestic hot water. I really ought to go solar for that.

Pre-paid contracts are a crap shoot price-wise and you have to really trust the supplier. For the past couple years it seems a few oil suppliers have gone bankrupt leaving their pre-paid customers in a bad way. I don't know if they get in over their heads with futures contracts or what.

I have used an electric space heater to take the chill off the shower bathroom just running it for 45 min. or so when showering, which is much cheaper (<20 cents/day), but we thought we would see what the radiant heat will do. It adds about 80 gals of propane to my annual usage but the floor is warm - which makes Sharon happy

Dave.

The shop is part of the same structure, has slightly leakier doors and 2" insulation instead of 4". There is no insulation under the shop slab. It got down to 36F in the depths of winter, but most of the time was 40 and above. Close as I can offer for your question. The shop gets a hot air panel for next winter. Amazingly simple things to put together.

Contract prices are better, assuming you use the predicted amount of propane. New house last summer, so that wasn't an option, I hope to greatly decrease usage this winter, so not this year either.

Steve

 

[SamWalton]

We moved in on May 30th. Our home is far from ready but we need to say enough is enough to paying $800 for a rundown rental which is worth about $600 in the Sallisaw market. We got our bathroom going with a shower laundry sink and a toilet. We paid $1328.68 for our Bradford White S-SW2-75R6DS indirect hot water heater, which is not installed yet because we received it late and installed a instant unit we will use under the bar later. We have been focusing all efforts to get the bath room online. We got most of the walls finished and the washer and dryer installed. We have a new stove, refrigerator and freezer but no other remnants of a kitchen. Well if you count a large picnic table and our dining room table. This is not the worst of it. Our home is still not covered with dirt because we are still dealing with a few leaks and uncertain of the secondary water proofing systems we will employ. The black stuff on the roof is adsorbing all the sun has to offer and making it tuff for us to handle the heat. We are trying to get a heat pump installed but most of the contractors are fishing for too much cash. Our other problem is that the new R410a looks to be another forced product through good old crony capitalism. I want to purchase a R22 5 ton heat pump with the variable speed blower. I also want to locate the outside unit about 75 feet away from the inside unit. This is because the design has the outside unit in the middle of the west berm wall and I am not sure what kind of slope we can get away with from roof to ground level. I am not sure if the size is right. If we size it to large it won't remove the humidity as needed. I would like to believe we are going to get 90% savings in heat and air but we will have earth on the roof and two modules west walls. I don't count the garage because we aren't providing any HVAC to this area.

 

[mjncad]

That's quite a collection of pets you have there Sam.

 

[MarkV]

Sam a 5 ton heat pump sounds kind of big for your place to me. We are running 1850 sq ft with 3 tons comfortably. Given your eventual insulation value I would think you would get by with less than 5 tons. I guess you realize that once existing stocks of R22 are depleted that no more can be produced.

MarkV

 

[SamWalton]

That's quite a collection of pets you have there Sam.

I hoping for a dog and got a whole lot more.

 

[SamWalton]

Sam a 5 ton heat pump sounds kind of big for your place to me. We are running 1850 sq ft with 3 tons comfortably. Given your eventual insulation value I would think you would get by with less than 5 tons. I guess you realize that once existing stocks of R22 are depleted that no more can be produced.

MarkV

We are heating and cooling 3045 SF based on the high ceiling and 2744 SF with no consideration for the high ceilings. One ton per 500 SF of living space. The R22 has a few other direct replacements like NU-22, R407c, R404a and R417a. The R410A has problems with moisture and pressure related issues. The manufacturers can sell new R22 equipment but it cant be pre-charged.